Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-11-01
2001-08-14
Fox, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C422S242000
Reexamination Certificate
active
06273134
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to sterilizers and more particularly, to an improved sterilizer valve.
BACKGROUND OF THE INVENTION
Autoclaves for sterilizing instruments, for example, dental and surgical instruments, have been used for decades. Of particular interest are freestanding, self-contained autoclave units similar to that illustrated in FIG.
10
. The prior art autoclave or sterilizer
20
includes a sterilizing chamber
22
surrounded by heaters, for example, band heaters (not shown). Upon placing the items to be sterilized in the chamber
22
, a user, via a control panel (not shown), initiates a sterilizing cycle the first step of which is to use the heaters to heat the sterilizing chamber to a temperature, for example, 275° F. Upon reaching that temperature, the user is signaled to turn the knob
26
which operates a valve
28
, sometimes referred to as a metering valve, thereby causing a known quantity of sterilizing fluid, for example, water or sterilizing chemicals, to flow from a shotwell
30
through tubing
32
into the chamber
22
. The sterilizing fluid immediately vaporizes, thereby producing a sterilizing steam or vapor which creates a vapor pressure of 20-40 pounds per square inch.
At the end of a sterilizing cycle, the operator is signaled to return the control knob
26
to its original position, and the valve
28
permits the sterilizing chamber
22
to be purged by a vacuum or pressurized air through a controlled vent system. Thus, the valve
28
functions as a two-way valve. The pressurized air is supplied to a purge inlet (not shown) of the sterilizing chamber
22
and forces the vapor from the sterilizing chamber
22
, through the tubing
32
, through the valve
28
, through a vent line
36
and into a condensing manifold
38
. The purged sterilizing vapors and fluid then pass through condensing and cooling coils
40
and into a waste tank
42
. The waste tank is vented via tubing
44
through a carbon filter
46
to atmosphere. The manifold
38
, coils
40
, waste tank
40
and filter
46
function together to form a controlled vent system in which the used sterilizing fluid and vapors are contained and processed so that waste materials are collected and clean air is discharged into the environment. The specific structure of a controller vent system will vary depending on the sterilizer, the sterilizing fluid, the items being sterilized and other factors. A sterilizer providing the sterilizing cycle just described is commercially available as a Chemiclave EC5500/EC6000 from Bamstead|Thermolyne Corporation of Dubuque, Iowa.
Of interest to the present invention is one known valve
28
which is shown as partially disassembled in FIG.
11
. The valve
28
has a shotwell
50
which is fluidly connected to a valve stem
52
that includes various passages
54
that are operatively coupled to passages within a valve body
56
, thereby interconnecting ports
58
in the appropriate manner to achieve the desired two-way valving action. A valve of the construction shown in
FIG. 11
has proven to have certain disadvantages. For example, the tapered sides
53
of the valve stem
52
must be machined to perfectly match the tapered sides
60
of a bore within the valve body
56
. The mating of the tapered sides
53
with the tapered sides
60
must provide a tight seal against the fluids and pressurized vapors passing through the valve
28
. Therefore, the tapered sides
53
,
60
must have very accurate manufacturing tolerances so that such a seal is achieved. Further, the tapered sides
53
on the valve stem
52
are also coated with a “TEFLON” material which is machined to provide the final taper to the desired accuracy. The valve body
56
is normally nickel plated to provide the desired hardness. The processes of applying the “TEFLON” coating and nickel plating are expensive and if not properly performed, can contribute to a malfunction of the valve
28
. The net result is that valves of such a design are difficult to manufacture and sometimes fail after a relatively short period of time.
The valve
28
provides only a single position of the valve body
56
with respect to the valve stem
52
at which the shotwell
50
is purged of any excessive pressurized sterilizing fluid and/or vapors. In that position, the vent holes
62
of the valve body
56
are aligned with the vent holes
54
, thereby purging pressurized vapors from the shotwell
50
directly into the atmosphere and bypassing the controlled vent system within the sterilizer used to vent the chamber
22
. With this valve construction, the shotwell is normally vented to atmosphere within the sterilizer housing. As will be appreciated, venting pressurized vapors within the sterilizer housing has several disadvantages. First, the vapors and fluid are hot and under pressure which results in such vapors and/or fluid being projected from the holes
62
into the housing of the sterilizer. Such spitting action of the sterilizing fluid and/or vapors is unpredictable. Not only is it undesirable to have an uncontained liquid within the sterilizer housing, but such vented vapors and liquid may present an undesirable odor, possibly facilitate corrosion and in some applications be volatile.
Another known valve
28
is shown partially disassembled in FIG.
12
. Valve components in
FIG. 12
that are common with those described earlier with respect to
FIG. 11
are commonly numbered. The valve stem
52
has a straight cylindrical side
57
, and slides into a cylindrical bore
59
within the valve body
56
. O-rings
61
are used to seal the valve stem
52
within the cylindrical bore
59
, and an O-ring
63
is used to seal the fluid connection between each of the passages
54
within the valve stem and passages (not shown) intersecting the bore
59
within the valve body
56
. While this design eliminates the problems associated with the tapered design of
FIG. 11
, the design of
FIG. 12
is not trouble-free. The O-rings
63
often swell from their contact with the fluid and steam within the sterilizer, thereby making the valve stem difficult to turn by hand. Further, during rotation of the valve stem
52
within the valve body
56
, as one of the compressed O-rings
63
passes over a leading edge of the passage openings within the bore
59
of the valve body
56
, a portion of that O-ring
63
expands slightly into the valve body passage openings. Upon further rotation of the valve stem
52
, that expanded portion of the O-ring
63
must pass over the trailing edge of the valve body passage opening and recompress. That action causes severe wear on the O-ring
63
; and over time, the useful life of the O-ring
63
is significantly shortened. The valve
28
illustrated in
FIG. 12
vents the shotwell
50
through holes
62
, and thus, has the same disadvantages in that regard as previously discussed with respect to the valve illustrated in FIG.
11
.
A further known valve
28
is shown partially disassembled in FIG.
13
. Valve components in
FIG. 13
that are common with those described above with respect to
FIGS. 11 and 12
are commonly numbered. The valve stem
52
has a curved surface
65
, and slides into a cylindrical bore
59
within the valve body
56
. O-rings
61
are used to seal the valve stem
52
within the cylindrical bore
59
. An annular rubber seal
69
extends through a sidewall of the valve body
56
, and has a curved end
71
that matches the curve of the surface
65
. The sterilizer valve illustrated in
FIG. 13
has essentially the same problems as the sterilizer valve illustrated in FIG.
12
.
Thus, there is a need for a sterilizer having an improved valve that provides more reliable long term operation.
SUMMARY OF THE INVENTION
The present invention provides an improved valve for a sterilizer that functions more reliably and has a longer life than prior valves. The valve of the present invention is more reliably manufactured with substantially fewer parts that must be reworked and/or scrapped than valves of prior designs. Further, the valve of the present inv
Edwards James R.
Lahey Francis J.
Leppert Kerry W.
Barnstead Thermolyne Corporation
Fox John
Wood Herron & Evans L.L.P.
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